When a conventional assembly task of a thing by using a robot arm, movement trajectory information of the robot arm is generated in advance (this is called teaching), and the robot arm reproduces the movement on the trajectory to repeat the task. The assembly task targeting a rigid body is rarely failed in the repetitive assembly task.
However, when the method is used in the assembly task targeting a flexible body, the task may be failed. Since flexible bodies have individual differences in manufacturing steps, collide with the thing after manufacturing, or are deformed by their own weights, the failure of the task occurs because a fluctuation of shape or orientation is larger in a flexible body than that in a rigid body.
Patent Literature 1 discloses a method in which a force sensor is fixed to the wrist of an assembly robot arm, values of forces at respective times in a teaching state are acquired, and the robot arm is moved to reproduce the values of the acquired forces in a replay state.